Raise extras Sundials floor to 6.5

[ChrisRackauckas-Claude]

Please ignore this PR until it has been reviewed by @ChrisRackauckas.

Raise extras Sundials floor from 6 to 6.5 on ModelingToolkit and ModelingToolkitBase.

Declared Sundials 6.0 / 6.2 restrict SciMLBase to ≤ 3.39.1. Live MTK requires SciMLBase ≥ 3.19 and MTKBase ≥ 1.63 requires SciMLBase ≥ 3.44, so those pins are unsatisfiable. First working registered Sundials on this graph is 6.5.0.

DataInterpolations extras 9 still resolves at 9.0.0 and is not changed.

Fail before

Isolated depot, Julia 1.10.11, Pkg.develop ModelingToolkit + pin Sundials 6.0.0 / 6.2.0:

RESOLVE_FAIL PKG=Sundials VER=6.0.0
 └─SciMLBase restricted by Sundials 6.0.0 to 2.119.0-3.39.1 — no versions left
    (MTK wants SciMLBase ≥ 3.19; MTKBase 1.63 wants ≥ 3.44)

RESOLVE_FAIL PKG=Sundials VER=6.2.0
 └─SciMLBase restricted by Sundials 6.2.0 to 2.119.0-3.39.1 — no versions left

Same unsat on Pkg.develop ModelingToolkitBase.

Pass after

RESOLVE_OK PKG=Sundials VER=6.5.0

First working registered version is 6.5.0, not 6.2.